Suspension Lift Frequently Asked Questions

FAQ Status
(Jan 8/99) - Still working on it, but need help with the Trailmaster section, plus info on body lifts.

General
Probably the most commonly asked question about the Nissan
W/D21 series of trucks is how to lift them. There are several kits on the market by different manufacturers that can achieve this goal

Control Arm and Torsion bar Lifts (e.g. Rancho, Superlift, Desert Steel)
The Pathfinder and Hardbody trucks have basically identical front suspensions, which are in turn very similar to the 720 front suspension. These are Independent Front Suspension (IFS) systems using double A-arms (or control arms) to locate the wheel, torsion bars for the spring, and shock absorbers.

The A-arms provide for a fixed, limited
range of up and down travel. Rubber bumpstops and physical
limitations restrict the A-arms from exceeding their travel
limits. One end of the torsion bars are attached to the lower
control arm; the other end attaches to adjusters located in a frame
crossmember.

By adjusting
the torsion bars, it is possible to lift the front end of the
vehicle. Small lifts (say less than 1") can probably be
accommodated this way without needing a lift kit. When you increase
the lift, the tires begin to camber negatively (top of tire moves
inward towards the body) and the upper ball joint also takes on
more of an angle from horizontal. These effect can cause wear on
the ball joint as well as take the camber out of the alignment
range, causing uneven tire wear.

By lifting this way, the clearance underneath the front
skidplate is increased. The drawback is that the front CV
joint angles are increased as well. The maximum joint angles
are the limiting factor for the amount of lift and have to be a
consideration if you want to increase the total travel by lowering
the bumpstops. CV joints are weaker at higher operating
angles.

Normally, this
should not be a big problem as the front joints are only used when
in 4WD because of the locking hubs used on the Nissan. In
contrast, other makes such as Toyota use a central axle disconnect
system in which the front joints are always turning and could
therefore wear out faster with the higher operating angles from an
A-arm lift.

The remedy for
this situation is a replacement upper control arm (UCA) kit. The replacement UCA is longer than the factory UCA to help push out
the tire and compensate for the increased negative camber.
The ball joint angle is also improved. For lifting the rear
to match, the Pathfinder kit comes with taller rear coil springs;
the Hardbody kit comes with longer shackles (Superlift) or
add-a-leafs (Rancho).

However, by adjusting the torsion bars, one sacrifices
downward travel for lift -- basically you are changing the rest or
equilibrium position of the suspension so that it is lower down in
its travel compared to the stock position. Hence if you lift
the truck 2", you lose the 2" of downward travel. The
Pathfinder has about 7" of total up and down travel (3.5" each
way), so if you lift 2", that means that you have only 1.5"
remaining down travel, but have 5.5" upward travel

The physical limit of this lift is of
course to lift so high that the upper control arm contacts the
bumpstop continuously. This results in a terrible ride
because there is no downward travel at all and the suspension is
continously bottoming (or is it topping out?). A more
practical limit is about 2-2.5" of lift over stock, which provides
some room for downward travel that is adequate for street
purposes. Thus most kits are listed as 2.5" lifts, though you
can run a lower lift if you prefer.

When lifting with the torsion bars, the ride will
become stiffer the higher you go. Opinions vary as to why,
but the usual one is that the amount of twist, or preload, on the
torsion bar increases the higher you go, so you are winding up the
spring tighter, so to speak. I've also noted that as you go
higher, the tires actually move inwards slightly, thus the
springing force has to push against the lateral grip of the
tires. The effective lever length of the control arm shortens
too, because the control arm forms a greater angle with horizontal. Whatever the reason, the unanimous opinion is that you will
notice a stiffer ride.

With
regards to suspension alignment, lifting with the torsion bars
creates a larger angle with the tie rods, which tends to pull the
tires inwards towards the body, causing a toe-in condition (front
of tires are closer to the body than the rear of the tires). This is easily fixed at an alignment shop.

The tougher problem is that caster and
camber can also change. These are corrected by the alignment
shop by adding or subtracting shims behind the upper control arm
spindle, which helps to adjust the control arm in relation to the
body and the other control arm. The control arms (at least
Superlift, in my experience) are constructed so that if you lift a
specific amount (around 2"), you will not have to adjust the caster
and camber, assuming that your stock suspension was properly
aligned to begin with.

In my last alignment, the shop did not bother
correcting the camber or caster, only the toe-in. I suspect
this is because of the extra work involved with having to remove
the tires in order to get to the spindle, or else that my specs
were close to spec (they were very close, but not quite perfect). All I know is that I will not be going back to them. You would be well served to make sure that the camber and caster
are indeed adjusted. You might have to pay extra to get all
three measurements in spec. In fact, my local Nissan dealer
charges extra for Pathfinders, which indicates that recognize the
additional work required. Make sure you get the before and
after specs to make sure the alignment meets factory
specifications.

I suspect
that some problems reported with lifts such as accelerated or
uneven tire wear may be due to the alignment shops and not directly
due to the quality of the kits themselves.

Trail Master 4"
SystemThe Trail
Master 4" lift system is much more involved than the control arm
lift. The TM kit includes bracketry to relocate the front
differential and lower control arm downwards, plus balljoint
spacers for the upper control arm. The mounting point for the
torsion bars is also relocated downwards below the level of the
frame. The rear lift consists of a coil spring spacer to
augment the factory coils.